1. Field of the Invention
The present invention generally relates to reversible, stepless, ratchet mechanisms.
2. Description of the Related Art
Various one way clutches are known which use frictional or wedging action to transmit torque. Most common is the use of ball roller bearings in a ramp or cam like assembly. The rollers are pressed between an inner core and an outer cylindrical housing during torque transmission. Negligible friction is present in the torque direction so the wedging action is transformed almost entirely to a radial force between the core and cylinder. Batten U.S. Pat. No. 3,398,612 is a typical example of a wedged roller design. Williams U.S. Pat. No. 5,136,901 shows a reversible wedged roller design. The direction selector rotates substantially around the turning axis of the clutch mechanism.
Fuller U.S. Pat. No. 4,485,699 shows a slide switch selectable wedged roller mechanism. Two oppositely acting roller clutches are separately engagable. Duplicate clutches are required in this design since the clutches cannot be internally reconfigured. Bramsiepe U.S. Pat. No. 5,069,091 employs roller elements and is direction selectable by rotating a cylindrical control element about the driven shaft.
A second clutch design method uses mostly frictional wedging or clamping action. Dodge U.S. Pat. No. 1,983,123 and Goldwater U.S. Pat. No. 2,735,324 employ a single wedgeable braking element. The element presses radially against the rotating core, causing the core to lock against the housing wall.
Rude U.S. Pat. No. 4,427,100 employs a torsion spring clutch. A rotatable control element loads the spring at one end or the other to cause a frictional clamping action.
Browning U.S. Pat. No. 3,061,061 employs a plate wedgeable between a cylindrical housing and a flat sided rotatable core. A spring bias allows the plate to rotate freely in one direction within the cylinder and to become wedged when forced the opposite direction by the flat side of the rotatable core. A selector element rotates about the core element, or driven shaft, to bias the spring in one direction or the other.
Stover U.S. Pat. No. 2,762,478 is similar to U.S. Pat. No. 3,061,061, except that U.S. Pat. No. 2,762,478 uses multiple wedgeable segments.
Walton, U.S. Pat. No. 2,870,889 includes a pair of opposed wedgeable clutch bars.
The present invention is especially intended for screwdriver type tools.
The present invention improves the design of direction selectable stepless clutches with an improved selection means and a simplified, low cost, design.
The controlling element is a slide switch, rather than the usual rotatable collar. A slide switch is most convenient when gripping a screwdriver type handle. A rotating cylinder switch usually requires a second hand to actuate it.
Unlike the slide switch of U.S. Pat. No. 4,485,699, the switch of the present invention acts upon a simple, simplified clutch element.
The clutch mechanism of the present invention improves upon that of U.S. Pat. No. 3,061,061. The wedgeable plate of the present invention is oriented radially rather than axially, relative to the output shaft. The plate can then be manufactured with high speed progressive die equipment to precisely follow the curve of the housing wall where the plate contacts the wall. The angled edges of the plate of U.S. Pat. No. 3,061,061 must be made with less efficient methods.
A further advantage of the present plate design is that it presents edges which may be easily contacted by an axially slidable element. Simple contours on the slidable element selectively press against such edges to provide a selectable spring bias. The slidable element rotates entirely within the tool handle housing. It is accessible from the exterior of the housing through a slide switch. The slide switch links to the slidable element through a circumferencial groove around the rotating element.
Unlike the tools of U.S. Pat. No. 3,051,061 and U.S. Pat. No. 5,069,091, the mechanism of the present invention presents no rotating components outside of the tool housing other than the output shaft. The housing can then have a fixed front bearing component rather than a rotating front bearing sleeve such as 12 in U.S. Pat. No. 3,061,061 or 10 in U.S. Pat. No. 5,069,091. The shaft is therefore more rigidly held within the housing of the present invention.
The present invention uses a deep drawn can, or closed end cylinder, to form the clutch housing wall and rear shaft containment bearing. This is more economical than the machined housing 4 in U.S. Pat. No. 3,061,061, thereby reducing the manufacturing cost. Housing 4 in U.S. Pat. No. 3,061,061 cannot be deep drawn since it has non-constant wall thicknesses between the front and rear portions and a "conically tapered end 7". The shallow closed end of the can of the present invention simplifies deep drawing and provides structural support to the side walls. Deep drawing has the further advantage of providing a high strength work hardened material. The same material cut from solid material must have thicker sections to show equal strength.